Significance of using " , " in neo4j multiple relationships cypher query

[clem]

This is a subtle point. The comma between two match clauses creates a cartesian product, which can be very expensive. That is:

MATCH condition1, condition2
...

creates every possible combination of conduction1 and conduction2.

But if you do:

MATCH condition1
MATCH condition2
...

you don't get a cartesian product.

For more info, see:

Avoid cartesian product when create relationships

If you collect them between matching them, sure: MATCH (a {property1:0}) WITH collect(a) as aNodes MATCH (b {property2:1}) WITH aNodes, collect(b) as bNodes (also you should be using labels, otherwise these will be expensive allNodesScans, two of them). So now you have a list of 100 a nodes and a list of 100 b nodes. To connect them to each other you either need two foreaches (one nested in the other), or to UNWIND both lists back to rows. That would get you a cartesian product as a result, b…